You can pry the Rapunzel and Hugo become besties headcanon from my cold, dead hands. And then you’ll fail because I’ll come back to life and rip it back.
Hugo has just gone through the biggest change in his life. He’s gone from street rat thief working under a crime lord, to the Royal Engineer and Royal Engineer’s boyfriend. He’s almost a part of the Coronan royal family. He’s trying to change and grow as a person. He’s navigating royal life, boyfriend life, and just life in general. He’s confused, he doesn’t know how to do this. He’s scared he’s going to slip up and everything will be taken from him. He’s hurting, from how much everything has changed and how much he misses his old life, and how he feels guilt for missing his old life. All of this on top of the guilt for hurting Varian that they just aren’t going to get over with a simple kiss.
Hugo’s scared and confused but Rapunzel is the first to accept him with open arms. She doesn’t see a traitor lowlife thief, she doesn’t see the boy who hurt her friend, all she sees is Hugo. A brilliant engineer who would do anything for Varian. Even if he lashes out at her, trying to justify his feelings by projecting onto the seemingly perfect princess, she wouldn’t give up on him. She never gives up on her friends and dammit, she’s going to be his friend. She sees someone who needs an unbiased and loving person who can guide him through the uncertainty and confusion of being suddenly thrust into royal life. She’s patient, and gentle. She doesn’t take Hugo’s sassiness to heart. And if he does hit a nerve, she can sass him back and humble him. (Which let’s be honest, would earn his respect even faster.)
Rapunzel would be such a good thing for Hugo because not only would she be a good friend for helping him navigate what she and Eugene went through, but she can help him navigate what she and Varian went through. She knows what it’s like to hurt Varian. She can help Hugo forgive himself, she can help him learn how to navigate talking to Varian about these things.
Rapunzel is also just a good match for Hugo, they’d have amazing chemistry. We already know she’s tough as nails and loves to joke around, she and Hugo would get along splendidly. She can help bring out his softer side and he can bring out her spunky and rebellious side. They can prank Eugene together. They can paint eachother’s nails. Hugo can be her styling mannequin. They can dye eachother’s hair. They can go on adventures together. They can gossip about the royal staff together. Rapunzel can be the friend Hugo desperately needs during this adjustment period.